Alternaria alternata causes leaf blight of rosy periwinkle (Catharanthus roseus) in Iraq
Nursery-grown rosy periwinkles (Catharanthus roseus) in Kerbala province, Iraq, showed severe symptoms of leaf blight. The causal agent associated with the diseased plants was identified as the fungus Alternaria alternata. This identification was based on the pathogen’s morphological, molecular and pathogenic characteristics. To the best of the author’s knowledge, leaf blight of rosy periwinkle caused by A. alternata is the first record in Iraq.
KeywordsAlternaria alternata Leaf blight Catharanthus roseus rDNA-ITS Iraq
Catharanthus roseus, known as rosy periwinkle or Madagascar periwinkle, is an annual or perennial evergreen herbal plant that is native from Madagascar (Stearn 1975). Nowadays, it is cultivated globally, including in Iraq, for its therapeutic and ornamental attractive features. It has an ornamental aesthetic appearance related to its green variegation and prolific flowers in splendid colors (Nejat et al. 2015). The plant is also a source of pharmaceutical compounds such as terpenoid indole alkaloids including vincristine and vinblastine that have valuable antitumor properties (Aslam et al. 2010).
Several phytopathogens have been reported to cause a variety of diseases on periwinkle plants worldwide. The majority of the fungal diseases recorded were root rot and damping-off incited by numerous fungi such as Rhizoctonia solani, Fusarium oxysporum, F. solani, Thielaviopsis sp., Sclerotinia sclerotiorum, Sclerotium rolfsii and Pythium aphanidermatum and foliar blight caused by Phytophthora parasitica, P. tropicalis, Colletotrichum dematium and Botrytis cinerea (Nejat et al. 2015; Ou-Yang and Wu 1998). However, there are no published studies relating to pathogens infecting periwinkle plants in Iraq.
During the growing season 2015/ 2016, severe symptoms of foliar blight were observed on rosy periwinkle in one of the main ornamental nurseries in Kerbala province, Iraq. The symptoms initiated as small circular to irregular light brown spots that gradually enlarged and darkened to cover most of the leaf surface. The diseased leaves ultimately became withered and dry leading to the death of the plant.
The fungal pathogen isolated from symptomatic leaves of rosy periwinkle was characterised to species level based on its morphological and molecular characteristics, which were similar to those of A. alternata.
Alternaria alternata has been reported as a fungus causing various diseases mainly leaf spot and blight on a wide range of plant hosts. It was, for example, reported as the cause of leaf spot of Musa spp., Actinidia deliciosa, Rumex vesicarius and Juglans regia (Parkunan et al. 2013; Corazza et al. 1999; Sankar et al. 2012; Belisario et al. 1999) and blight of Zinnia acerosa, Artemisia annua, Incarvillea emodi and Zanthoxylum piperitum (Colbaugh et al. 2001; Samanta et al. 2009; Shanmugam et al. 2011; Yang et al. 2013). Additionally, A. alternata was reported as an endophytic fungus on Catharanthus roseus (Kharwar et al. 2008; Momsia and Momsia 2013; Palem et al. 2015). However, there is no previous report relating this pathogen to disease on rosy periwinkle plants in Iraq. Hence, this is the first report of A. alternata causing leaf blight of rosy periwinkle.
The author would like to acknowledge Dr. Jennie Brierley for proofreading and the Plant protection Department/Agriculture College/University of Kerbala for using of the facilities.
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